This invention relates to electrical connectors. More particularly, the invention relates to zero insertion force pin grid array sockets for use in connecting an integrated circuit to a circuit substrate.
A pin grid array (PGA) socket is used for connecting an integrated circuit (IC), such as an application-specific integrated circuit (ASIC), to a circuit substrate, such as a printed circuit board (PCB). PGA sockets typically comprise a base that supports a plurality of contacts, and a cover that includes a plurality of insertion holes. The base is mounted on the circuit substrate to form an electrical connection with circuits on the circuit substrate. The cover is attached to the base prior to assembly of the circuit substrate so that the lateral surfaces of the circuit substrate, base, and cover are stacked in a parallel arrangement.
Typical PGA socket covers have rows and columns of insertion holes. The exact number of insertion holes and the orientation of the insertion holes typically depends on the types of ICs to be connected to the circuit substrate. The rows and columns of insertion holes are spaced on interstitial centers calculated to accommodate the pin densities of the ICs. Currently available ICs can have pins spaced on about 0.05-inch centers or less.
Historically, when it was desired to connect an IC to a circuit substrate, the pins of the IC were forcibly inserted into the insertion holes of the cover and against the contacts to form an electrical connection between the pins of the IC and the electrically conductive contacts. It was found that the insertion force required to establish an adequate electrical connection is considerable and can lead to difficulty in installing and removing the IC. Moreover, the pins of the IC can be damaged easily as a result of its installation and removal.
Therefore, low insertion force (LIF) and zero insertion force (ZIF) PGA sockets have been developed to reduce the insertion forces needed to establish an electrical connection between the contacts and the pins. The covers of LIF or ZIF PGA sockets are typically attached to the base so that the cover is movable over the lateral surface of the base. An actuator or other mechanism for camming the cover over the surface of the base is included so that the contacts are deflected against the pins of the IC. The base cover can have contact support walls for supporting the individual contacts.
These LIF and ZIF devices, however, also can cause the pins of the ICs to be damaged. For example, as the cover moves over the surface of the base, the portion of the pins extending beneath the cover can be forced against the contacts. This can create a shear force and a moment which cause the pins to bend or to break. Additionally, the mating force between the contact and the pin can damage the pin since the pins themselves are not provided with any support in the mating region.
Therefore, there is a need for a ZIF PGA socket that can be used to connect an IC to a circuit substrate without causing the portion of the pins extending beneath the cover to be forced against the contacts, thus reducing the incidence of pin damage. Moreover, the ZIF PGA socket should be compatible with ICs having pins spaced on 0.05-inch centers or less.
According to the present invention, a socket for connecting to a circuit substrate an electrical component having a terminal extending along a terminal axis therefrom comprises a base, a contact secured to the base to electrically connect the terminal to the circuit substrate, a cover attached to the base, and an actuator.
The contact comprises a beam portion elongated along a beam axis, and a contact mating portion having a contact aperture therein to receive the terminal. The contact mating portion is flexibly connected to an end of the beam portion, and defines a contact plane at an angle with the beam axis. Preferably, this angle is about 90 degrees or less. The aperture through the contact mating portion can have a substantially circular cross-section, and the beam portion can have a substantially uniform cross-sectional area along a length thereof. The contact mating portion and beam portion can be integrally formed with one another by stamping, for example, from a sheet of electrically conductive material.
The cover is attached to the base and has a lead-in aperture for receiving the terminal and allowing the terminal to enter the contact aperture. The actuator is operatively coupled to the contact, for causing the contact mating portion to rotate and to engage the terminal.
The socket of the present invention can also include a deflection member extending from an inner surface of the cover proximate the lead-in aperture, for causing the contact mating portion to rotate. The deflection member can extend from the inner surface of the cover, for causing the contact mating portion to rotate relative to the terminal axis when the cover is moved toward the base. Alternatively, the deflection member can extend from the inner surface of the cover, for causing the contact mating portion to rotate relative to the terminal axis when the cover is moved along the base. The deflection member can also have an aperture through which the beam element extends, for causing the contact mating portion to rotate relative to the pin axis when the deflection member is moved relative to the beam element.
According to the present invention, a method of electrically connecting to a circuit substrate an electrical component having a terminal extending therefrom comprises providing a socket connector having a contact with a contact mating portion that has a contact aperture therethrough, and actuating the mating portion from an open position, in which the contact aperture freely accepts the terminal, to a closed position, in which an edge defining the contact aperture is in electrical contact with the terminal.